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A search for new phenomena in pp collisions at ?s=13TeV in final states with missing transverse momentum and at least one jet using the ?T variable
(Springer, 2017) Khachatryan, V.; Sirunyan, A. M.; Tumasyan, A.; Adam, W.; Asilar, E.; Bergauer, T.; The CMS Collaboration
A search for new phenomena is performed in final states containing one or more jets and an imbalance in transverse momentum in pp collisions at a centre-of-mass energy of 13 TeV. The analysed data sample, recorded with the CMS detector at the CERN LHC, corresponds to an integrated luminosity of 2.3 fb(-1). Several kinematic variables are employed to suppress the dominant background, multijet production, as well as to discriminate between other standard model and new physics processes. The search provides sensitivity to a broad range of new-physics models that yield a stable weakly interacting massive particle. The number of observed candidate events is found to agree with the expected contributions from standard model processes, and the result is interpreted in the mass parameter space of fourteen simplified supersymmetric models that assume the pair production of gluinos or squarks and a range of decay modes. For models that assume gluino pair production, masses up to 1575 and 975 GeV are excluded for gluinos and neutralinos, respectively. For models involving the pair production of top squarks and compressed mass spectra, top squark masses up to 400 GeV are excluded.
A search for pair production of new light bosons decaying into muons
(Elsevier, 2016) Khachatryan, V.; Sirunyan, A. M.; Tumasyan, A.; Adam, W.; Asilar, E.; Bergauer, T.; The CMS Collaboration
A search for the pair production of new light bosons, each decaying into a pair of muons, is performed with the CMS experiment at the LHC, using a dataset corresponding to an integrated luminosity of 20.7 fb(-1) collected in proton-proton collisions at center-of-mass energy of root s = 8 TeV. No excess is observed in the data relative to standard model background expectation and a model independent upper limit on the product of the cross section, branching fraction, and acceptance is derived. The results are compared with two benchmark models, the first one in the context of the next-to-minimal super-symmetric standard model, and the second one in scenarios containing a hidden sector, including those predicting a nonnegligible light boson lifetime. (C) 2015 CERN for the benefit of the CMS Collaboration. Published by Elsevier B.V.
Alignment of the CMS tracker with LHC and cosmic ray data
(Iop Publishing Ltd, 2014) Chatrchyan, S.; Khachatryan, V.; Sirunyan, A. M.; Tumasyan, A.; Adam, W.; Bergauer, T.; The CMS Collaboration
The central component of the CMS detector is the largest silicon tracker ever built. The precise alignment of this complex device is a formidable challenge, and only achievable with a significant extension of the technologies routinely used for tracking detectors in the past. This article describes the full-scale alignment procedure as it is used during LHC operations. Among the specific features of the method are the simultaneous determination of up to 200 000 alignment parameters with tracks, the measurement of individual sensor curvature parameters, the control of systematic misalignment effects, and the implementation of the whole procedure in a multiprocessor environment for high execution speed. Overall, the achieved statistical accuracy on the module alignment is found to be significantly better than 10 mu m.
Angular analysis and branching fraction measurement of the decay B0 ? K*0?+?-
(Elsevier, 2013) Chatrchyan, S.; Khachatryan, V.; Sirunyan, A. M.; Tumasyan, A.; Adam, W.; Bergauer, T.; The CMS Collaboration
The angular distributions and the differential branching fraction of the decay B-0 -> K*(892)(0)mu(+)mu(-) are studied using a data sample corresponding to an integrated luminosity of 5.2 fb(-1) collected with the CMS detector at the LHC in pp collisions at root s = 7 TeV. From more than 400 signal decays, the forward-backward asymmetry of the muons, the K*(892)(0) longitudinal polarization fraction, and the differential branching fraction are determined as a function of the square of the dimuon invariant mass. The measurements are in good agreement with standard model predictions. (C) 2013 CERN. Published by Elsevier B.V. All rights reserved.
Angular analysis of the decay B0 ? K*0?+?- from pp collisions at ?s=8 TeV
(Elsevier, 2016) Khachatryan, V.; Sirunyan, A. M.; Tumasyan, A.; Adam, W.; Asilar, E.; Bergauer, T.; The CMS Collaboration
The angular distributions and the differential branching fraction of the decay B-0 -> K*(892)(0)mu(+)mu(-) are studied using data corresponding to an integrated luminosity of 20.5 fb(-1) collected with the CMS detector at the LHC in pp collisions at root s = 8 TeV. From 1430 signal decays, the forward-backward asymmetry of the muons, the K*(892)(0) longitudinal polarization fraction, and the differential branching fraction are determined as a function of the dimuon invariant mass squared. The measurements are among the most precise to date and are in good agreement with standard model predictions. (C) 2015 CERN for the benefit of the CMS Collaboration. Published by Elsevier B.V. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/).
Angular coefficients of Z bosons produced in pp collisions at ?S=8 TeV and decaying to ?+?- as a function of transverse momentum and rapidity
(Elsevier, 2015) Khachatryan, V.; Sirunyan, A. M.; Tumasyan, A.; Adam, W.; Bergauer, T.; Dragicevic, M.; The CMS Collaboration
Measurements of the five most significant angular coefficients, A(0) through A(4), for Z bosons produced in pp collisions at root S = 8 TeV and decaying to mu(+)mu(-) are presented as a function of the transverse momentum and rapidity of the Z boson. The integrated luminosity of the dataset collected with the CMS detector at the LHC corresponds to 19.7 fb(-1). These measurements provide comprehensive information about the Z boson production mechanisms, and are compared to the QCD predictions at leading order, next-to-leading order, and next-to-next-to-leading order in perturbation theory. (C) 2015 CERN for the benefit of the CMS Collaboration. Published by Elsevier B.V.
Azimuthal decorrelation of jets widely separated in rapidity in pp collisions at ?s=7 TeV
(Springer, 2016) Khachatryan, V.; Sirunyan, A. M.; Tumasyan, A.; Adam, W.; Asilar, E.; Bergauer, T.; The CMS Collaboration
The decorrelation in the azimuthal angle between the most forward and the most backward jets (Mueller-Navelet jets) is measured in data collected in pp collisions with the CMS detector at the LHC at root s = 7 TeV. The measurement is presented in the form of distributions of azimuthal-angle differences, Delta phi, between the Mueller-Navelet jets, the average cosines of (pi - Delta phi), 2(pi - Delta phi), and 3(pi - Delta phi), and ratios of these cosines. The jets are required to have transverse momenta, p(T), in excess of 35 GeV and rapidities, |y|, of less than 4.7. The results are presented as a function of the rapidity separation, Delta y, between the Mueller-Navelet jets, reaching Delta y up to 9.4 for the first time. The results are compared to predictions of various Monte Carlo event generators and to analytical predictions based on the DGLAP and BFKL parton evolution schemes.
Charged-particle nuclear modification factors in PbPb and pPb collisions at ?sNN=5.02 TeV
(Springer, 2017) Khachatryan, V.; Sirunyan, A. M.; Tumasyan, A.; Adam, W.; Asilar, E.; Bergauer, T.; The CMS Collaboration
The spectra of charged particles produced within the pseudorapidity window vertical bar eta vertical bar < 1 at root s(NN) = 5 : 02 TeV are measured using 404 mu b(-1) of PbPb and 27.4 pb(-1) of pp data collected by the CMS detector at the LHC in 2015. The spectra are presented over the transverse momentum ranges spanning 0 : 5 < p(T) < 400 GeV in pp and 0 : 7 < p(T) < 400 GeV in PbPb collisions. The corresponding nuclear modification factor, R-AA, is measured in bins of collision centrality. The R-AA in the 5% most central collisions shows a maximal suppression by a factor of 7-8 in the p(T) region of 6-9 GeV. This dip is followed by an increase, which continues up to the highest p(T) measured, and approaches unity in the vicinity of p(T) = 200 GeV. The R-AA is compared to theoretical predictions and earlier experimental results at lower collision energies. The newly measured pp spectrum is combined with the pPb spectrum previously published by the CMS collaboration to construct the pPb nuclear modification factor, R-pA, up to 120 GeV. For p(T) > 20 GeV, R-pA exhibits weak momentum dependence and shows a moderate enhancement above unity.
Coherent J/? photoproduction in ultra-peripheral PbPb collisions at ?sNN=2.76 TeV with the CMS experiment
(Elsevier, 2017) Khachatryan, V.; Sirunyan, A. M.; Tumasyan, A.; Adam, W.; Asilar, E.; Bergauer, T.; The CMS Collaboration
The cross section for coherent J/psi photoproduction accompanied by at least one neutron on one side of the interaction point and no neutron activity on the other side, Xn0n, is measured with the CMS experiment in ultra-peripheral PbPb collisions at root sNN= 2.76TeV. The analysis is based on a data sample corresponding to an integrated luminosity of 159 mu b(-1), collected during the 2011 PbPb run. The J/psi mesons are reconstructed in the dimuon decay channel, while neutrons are detected using zero degree calorimeters. The measured cross section is d sigma(Xn)o(n)(coh)/dy(J/psi) = 0.36 +/- 0.04 (stat)+/- 0.04 (syst) mbin the rapidity interval 1.8
Comparison of the Z/?* + jets to ? + jets cross sections in pp collisions at ?s = 8 (vol 10, 128, 2015)
(Springer, 2016) Khachatryan, V.; Sirunyan, A. M.; Tumasyan, A.; Adam, W.; Asilar, E.; Bergauer, T.; The CMS Collaboration
[Abstract Not Available]
Comparison of the Z/?* plus jets to ? plus jets cross sections in pp collisions at ?s=8 TeV
(Springer, 2015) Khachatryan, V.; Sirunyan, A. M.; Tumasyan, A.; Adam, W.; Asilar, E.; Bergauer, T.; The CMS Collaboration
A comparison of the differential cross sections for the processes Z/gamma* + jets and photon (gamma)+ jets is presented. The measurements are based on data collected with the CMS detector at root s = 8TeV corresponding to an integrated luminosity of 19.7 fb(-1). The differential cross sections and their ratios are presented as functions of p(T). The measurements are also shown as functions of the jet multiplicity. Differential cross sections are obtained as functions of the ratio of the Z/gamma* p(T) to the sum of all jet transverse momenta and of the ratio of the Z/gamma* p(T) to the leading jet transverse momentum. The data are corrected for detector effects and are compared to simulations based on several QCD calculations.
Constraints on parton distribution functions and extraction of the strong coupling constant from the inclusive jet cross section in pp collisions at ?s=7TeV
(Springer, 2015) Khachatryan, V.; Sirunyan, A. M.; Tumasyan, A.; Adam, W.; Bergauer, T.; Dragicevic, M.; The CMS Collaboration
The inclusive jet cross section for proton-proton collisions at a centre-of-mass energy of 7 TeV was measured by the CMS Collaboration at the LHC with data corresponding to an integrated luminosity of 5.0 fb(-1). The measurement covers a phase space up to 2 TeV in jet transverse momentum and 2.5 in absolute jet rapidity. The statistical precision of these data leads to stringent constraints on the parton distribution functions of the proton. The data provide important input for the gluon density at high fractions of the proton momentum and for the strong coupling constant at large energy scales. Using predictions from perturbative quantum chromodynamics at next-to-leading order, complemented with electroweak corrections, the constraining power of these data is investigated and the strong coupling constant at the Z boson mass M-Z is determined to be alpha(S)(M-Z) = 0.1185 +/- 0.0019 (exp)(-0.0037)(+0.0060) (theo), which is in agreement with the world average.
Constraints on the Higgs boson width from off-shell production and decay to Z-boson pairs
(Elsevier, 2014) Khachatryan, V.; Sirunyan, A. M.; Tumasyan, A.; Adam, W.; Bergauer, T.; Dragicevic, M.; The CMS Collaboration
Constraints are presented on the total width of the recently discovered Higgs boson, Gamma(H), using its relative on-shell and off-shell production and decay rates to a pair of Z bosons, where one Z boson decays to an electron or muon pair, and the other to an electron, muon, or neutrino pair. The analysis is based on the data collected by the CMS experiment at the LHC in 2011 and 2012, corresponding to integrated luminosities of 5.1 fb(-1) at a center-of-mass energy root s = 7 TeV and 19.7 fb(-1) at root s = 8 TeV. A simultaneous maximum likelihood fit to the measured kinematic distributions near the resonance peak and above the Z-boson pair production threshold leads to an upper limit on the Higgs boson width of Gamma(H) < 22 MeV at a 95% confidence level, which is 5.4 times the expected value in the standard model at the measured mass of m(H) = 125.6 GeV. (C) 2014 The Authors. Published by Elsevier B.V.
Constraints on the pMSSM, AMSB model and on other models from the search for long-lived charged particles in proton-proton collisions at ?s=8TeV
(Springer, 2015) Khachatryan, V.; Sirunyan, A. M.; Tumasyan, A.; Adam, W.; Bergauer, T.; Dragicevic, M.; The CMS Collaboration
Stringent limits are set on the long-lived lepton-like sector of the phenomenological minimal supersymmetric standard model (pMSSM) and the anomaly-mediated super-symmetry breaking (AMSB) model. The limits are derived from the results presented in a recent search for long-lived charged particles in proton-proton collisions, based on data collected by the CMS detector at a centre-of-mass energy of 8 TeV at the Large Hadron Collider. In the pMSSM parameter sub-space considered, 95.9% of the points predicting charginos with a lifetime of at least 10 ns are excluded. These constraints on the pMSSM are the first obtained at the LHC. Charginos with a lifetime greater than 100 ns and masses up to about 800 GeV in the AMSB model are also excluded. The method described can also be used to set constraints on other models.
Constraints on the spin-parity and anomalous HVV couplings of the Higgs boson in proton collisions at 7 and 8 TeV
(Amer Physical Soc, 2015) Khachatryan, V.; Sirunyan, A. M.; Tumasyan, A.; Adam, W.; Bergauer, T.; Dragicevic, M.; The CMS Collaboration
The study of the spin-parity and tensor structure of the interactions of the recently discovered Higgs boson is performed using the H -> ZZ, Z gamma*, gamma*gamma* -> 4l, H -> WW -> l(nu)l(nu), and H -> gamma gamma decay modes. The full data set recorded by the CMS experiment during the LHC run 1 is used, corresponding to an integrated luminosity of up to 5.1 fb(-1) at a center-of-mass energy of 7 TeV and up to 19.7 fb(-1) at 8 TeV. A wide range of spin-two models is excluded at a 99% confidence level or higher, or at a 99.87% confidence level for the minimal gravitylike couplings, regardless of whether assumptions are made on the production mechanism. Any mixed-parity spin-one state is excluded in the ZZ and WW modes at a greater than 99.999% confidence level. Under the hypothesis that the resonance is a spin-zero boson, the tensor structure of the interactions of the Higgs boson with two vector bosons ZZ, Z gamma, gamma gamma, and WW is investigated and limits on eleven anomalous contributions are set. Tighter constraints on anomalous HVV interactions are obtained by combining the HZZ and HWW measurements. All observations are consistent with the expectations for the standard model Higgs boson with the quantum numbers J(PC) = 0(++).
Correlations between jets and charged particles in PbPb and pp collisions at ?sNN=2.76 TeV
(Springer, 2016) Khachatryan, V.; Sirunyan, A. M.; Tumasyan, A.; Adam, W.; Asilar, E.; Bergauer, T.; The CMS Collaboration
The quark-gluon plasma is studied via medium-induced changes to correlations between jets and charged particles in PbPb collisions compared to pp reference data. This analysis uses data sets from PbPb and pp collisions with integrated luminosities of 166 mu b(-1) and 5.3 pb(-1), respectively, collected at root s(NN) = 2.76 TeV. The angular distributions of charged particles are studied as a function of relative pseudorapidity (Delta eta) and relative azimuthal angle (Delta phi) with respect to reconstructed jet directions. Charged particles are correlated with all jets with transverse momentum (p(T)) above 120 GeV, and with the leading and subleading jets (the highest and second-highest in p(T), respectively) in a selection of back-to-back dijet events. Modifications in PbPb data relative to pp reference data are characterized as a function of PbPb collision centrality and charged particle p(T). A centrality-dependent excess of low-p(T) particles is present for all jets studied, and is most pronounced in the most central events. This excess of low-p(T) particles follows a Gaussian-like distribution around the jet axis, and extends to large relative angles of Delta eta approximate to 1 and Delta phi approximate to 1.
Decomposing transverse momentum balance contributions for quenched jets in PbPb collisions at ?sNN=2.76 TeV
(Springer, 2016) Ruiz Vargas, J. C.; Khachatryan, V.; Sirunyan, A. M.; Tumasyan, A.; Adam, W.; Asilar, E.; The CMS Collaboration
Interactions between jets and the quark-gluon plasma produced in heavy ion collisions are studied via the angular distributions of summed charged-particle transverse momenta (p(T)) with respect to both the leading and subleading jet axes in high-p(T) dijet events. The contributions of charged particles in different momentum ranges to the overall event p(T) balance are decomposed into short-range jet peaks and a long-range azimuthal asymmetry in charged-particle p(T). The results for PbPb collisions are compared to those in pp collisions using data collected in 2011 and 2013, at collision energy root s(NN) = 2.76 TeV with integrated luminosities of 166 mu b(-1) and 5.3 pb(-1), respectively, by the CMS experiment at the LHC. Measurements are presented as functions of PbPb collision centrality, charged-particle p(T), relative azimuth, and radial distance from the jet axis for balanced and unbalanced dijets.
Description and performance of track and primary-vertex reconstruction with the CMS tracker
(Iop Publishing Ltd, 2014) Chatrchyan, S.; Khachatryan, V.; Sirunyan, A. M.; Tumasyan, A.; Adam, W.; Bergauer, T.; The CMS Collaboration
A description is provided of the software algorithms developed for the CMS tracker both for reconstructing charged-particle trajectories in proton-proton interactions and for using the resulting tracks to estimate the positions of the LHC luminous region and individual primary-interaction vertices. Despite the very hostile environment at the LHC, the performance obtained with these algorithms is found to be excellent. For t (t) over bar events under typical 2011 pileup conditions, the average track-reconstruction efficiency for promptly-produced charged particles with transverse momenta of p(T) > 0.9GeV is 94% for pseudorapidities of vertical bar eta vertical bar < 0.9 and 85% for 0.9 < vertical bar eta vertical bar < 2.5. The inefficiency is caused mainly by hadrons that undergo nuclear interactions in the tracker material. For isolated muons, the corresponding efficiencies are essentially 100%. For isolated muons of p(T) = 100GeV emitted at vertical bar eta vertical bar < 1.4, the resolutions are approximately 2.8% in p(T), and respectively, 10 m m and 30 mu m in the transverse and longitudinal impact parameters. The position resolution achieved for reconstructed primary vertices that correspond to interesting pp collisions is 10-12 mu m in each of the three spatial dimensions. The tracking and vertexing software is fast and flexible, and easily adaptable to other functions, such as fast tracking for the trigger, or dedicated tracking for electrons that takes into account bremsstrahlung.
Determination of the top-quark pole mass and strong coupling constant from the t(t)over-bar production cross section in pp collisions at ?s=7 TeV
(Elsevier, 2014) Chatrchyan, S.; Khachatryan, V.; Sirunyan, A. M.; Tumasyan, A.; Adam, W.; Bergauer, T.; The CMS Collaboration
The inclusive cross section for top-quark pair production measured by the CMS experiment in protonproton collisions at a center-of-mass energy of 7 TeV is compared to the QCD prediction at next-to-next-to-leading order with various parton distribution functions to determine the top-quark pole mass, m(t)(pole), or the strong coupling constant, alpha(S). With the parton distribution function set NNPDF2.3, a pole mass of 176.7(-3.4)(+3.8) GeV is obtained when constraining alpha(S) at the scale of the Z boson mass, m(Z), to the current world average. Alternatively, by constraining m(t)(pole) to the latest average from direct mass measurements, a value of alpha(S)(m(Z)) = 0.1151(-0.0032)(+0.0033) is extracted. This is the first determination of alpha(S) using events from top-quark production. (C) 2013 The Authors. Published by Elsevier B.V. All rights reserved.
Differential cross section measurements for the production of a W boson in association with jets in proton-proton collisions at ?s=7 TeV
(Elsevier, 2015) Khachatryan, V.; Sirunyan, A. M.; Tumasyan, A. .; Adam, W.; Bergauer, T.; Dragicevic, M.; The CMS Collaboration
Measurements are reported of differential cross sections for the production of a W boson, which decays into a muon and a neutrino, in association with jets, as a function of several variables, including the transverse momenta (p(T)) and pseudorapidities of the four leading jets, the scalar sum of jet transverse momenta (H-T), and the difference in azimuthal angle between the directions of each jet and the muon. The data sample of pp collisions at a centre-of-mass energy of 7 TeV was collected with the CMS detector at the LHC and corresponds to an integrated luminosity of 5.0 fb (1). The measured cross sections are compared to predictions from Monte Carlo generators, MADGRAPH + PYTHIA and SHERPA, and to next-to-leading-order calculations from BLACKHAT + SHERPA. The differential cross sections are found to be in agreement with the predictions, apart from the p(T) distributions of the leading jets at high p(T) values, the distributions of the H-T at high-H-T and low jet multiplicity, and the distribution of the difference in azimuthal angle between the leading jet and the muon at low values. (C) 2014 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/3.0/).

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